1. Field of the Invention
The present invention relates to a surge arrester arrangement comprising a surge arrester and a a cut-out device arranged in series with the arrester for automatic disconnection of the arrester in the event of an arrester failure.
2. The Prior Art
Surge arresters with cut-out devices are previously known, for example from U.S. Pat. No. 2,305,436 and EP-B-0 013 401, and are used, inter alia, in transmission lines to protect against back flashover caused by thunder or against switching surges. The arresters are placed in the towers of the transmission line and are connected between the respective phase line and the grounded tower construction. For a surge arrester connected between phase and ground, a failure in all probability results in a permanent ground fault. However, if the arrester is provided with a cut-out device which automatically disconnects the arrester in the event of a failure, the operation of the line can continue and the faulted arrester can be located and replaced at some suitable time. It is, however, important that the disconnected connection between the line and the arrester does not get near the line in case of hard wind, thus causing a ground fault on the line. Hitherto, there has been no good solution to this problem, and it is therefore common to arrange in line surge arresters, instead of cut-out devices, an open spark gap in series with the arrester. However, this normally provides an inferior protective effect, since it is difficult, from the point of view of voltage, to coordinate an arrester and a series-connected, separate spark gap. Another drawback with this solution is that there is no indication if the arrester has failed.